window.onload = function(){
	
	// 监听浏览器尺寸
	var isSet = false;
	window.onresize=function(){
		if(document.body.clientWidth > 1200){
			if(isSet){
				document.body.className = '';
				isSet = false;
			}
		}else{
			if(!isSet){
				document.body.className = 'w990';
				isSet = true;
			}
		}
	}
	
}